Process for dyeing cellulose acetate silk in fast black shades



Patented Mar. 29, 1932 ARGHIBALD JOHN HALL, or conenn'ron, .nnennnn, assmma m bi srnrnes BLEACHING & DYEING coiurnnvmrnrrnnson ,conennmon, .nner snn PROCESS non DYEING cnLLULosn Acnrn'rn s nk in res n BLACK 1% Drawing. Application filed August 2c, 1929, Serial No..3 88;635',;ant1.in emeaejfnneaiafdctaber 2.19281 V This invention relates to the dyeing of black shades of exceptional fastness on cellu-. lose acetate silk.

I have discovered, and this discovery forms the basis of this invention, that when cellulose acetate silk treated with solutions or colloidal dispersions of alpha-naphthylamine so as to absorb the alpha-naphthylamine is atterwards treated with solutions containing nitrous acid, the silk develops a deep black shade which has outstanding fastness to light, washing, rubbing, acids, alkalis, oxidizing and reducing agents.

I am aware that black shades may be produced on cellulose acetate silk by dyeing it with a suitable amino compound and then diazotizing with nitrous acid and coupling with a suitable naphthol such as beta-oxynaphthoic acid, but my invention diiiers entirely from such methods and the black resulting from our invention is much faster and cheaper to produce.

The action of nitrous acid on cellulose acetate silk containing alpha-naphthylarnine is :6 largely dependent on the concentration, acidity, and temperature of the nitrous acid solution. Under certain conditions, particularly when the concentration of the nitrous acid is very small or the acidity of the solution is low, a brownish black shade results. But

provided suitable conditions are employed the resulting black shade has a very pleasing tone.

I find that a satisfactory black shade is 85 produced when the action of the nitrous acid is nearly complete in from 5 to 10 minutes but it is to be understood that the length of time in which the cellulose acetate silk 7 should be immersed in the nitrous acid solution and/or the strength or" such solution depends upon the nature of the cellulose ac-. Thus in the case of" 'etate silk material.

yarn, a yarn having more twist will require a stronger solution if it is to penetrate the yarn in the same time as a yarn having less twist or if the same concentration isem ployed the'penetration will require a longer time. Similar in a woven or knitted fabric the strength of the nitrous acid solution and/or the length of time for penetration grams naphthylamine will depend both on the-twist the yarn Example One gram of alpha-naphthylamine is dissolved in 5 grams of warm oleic acid and the resulting solution diluted with 150 c. c. of warm water containing a" small amountof ammonia. silk areimmersed in this solution at a temperature of thoroughly washed with warm immersed for. 5'to 10 minutes in a solution ata temperature 0 containing 1 gram of sodium nitrite and 5 of sulphuric acid per c. c. The cellulose acetate silk thereby acquires a deep water, and c, c. of

black shade and is afterwards, rinsed, soaped, rinsed and dried.

It is believed that the black igment formed within the cellulose acetate bres by the process hereinbefore described has the character of an oxidation product of alpha naphthylamine in which a number of naphthalene residues are linked together by means of imino groups.

be clearly understood that the conditions stated therein are byway for applying my inven- Five grams of cellulose acetate C. for one hour, then What I cla m as invention and desire" to protect by Letters Patent is -1. Process for producing black shadeson I cellulose acetate silk which consists in first treating the cellulose acetate silk with alpha so that the latter will'be ab sorbed by the silk and subsequently treating the silk'with nitrous acid for the development'of a black shade thereon.

2. Process cellulose acetate silk silk containing absorbed alpha-naphthylfor producing black shades ony I which consists in first. V treating the cellulose acetate silk with colloir dal dispersions of alpha-naphthylamineso,

absorbed by theisilk silk with nitrous aclddor the development of a black treating cellulose acetate 1 cellulose acetate silk which consists in forming an oxidation product of alpha-naphthylamine ithin thecellulose acetatefibres by the action of nitrous acid on alpha-naphthylamine, v j. v

Intestimony whereof I have hereunto set my hand, this 15th day ofAugust, 1929.

AROHIBALD JOHN HALL 

